Tobacco can be enjoyed by adult tobacco consumers in a variety of forms. Smoking tobacco is combusted and the aerosol either tasted or inhaled (e.g., in a cigarette, cigar, or pipe). Smokeless tobacco products are not combusted and include: chewing tobacco, moist smokeless tobacco, snus, and dry snuff. Chewing tobacco is coarsely divided tobacco leaf that is typically packaged in a large pouch-like package and used in a plug or twist. Moist smokeless tobacco is a moist, more finely divided tobacco that is provided in loose form or in pouch form and is typically packaged in round cans and used as a pinch or in a pouch placed between an adult tobacco consumer's cheek and gum. Snus is a heat treated smokeless tobacco. Dry snuff is finely ground tobacco that is placed in the mouth or used nasally.
Nicotine is a component of various tobacco products. Over the years, however, various methods and systems have been developed for providing nicotine to adult consumers without the presence of tobacco plant tissue. Some ways tobacco-free nicotine is provided include transdermal patches, lozenges, and nicotine chewing gums.
Nicotine, or 3-(1-methyl-2-pyrrolidinyl)pyridine, is a tertiary amine with the following structure:

Under ambient conditions, nicotine is an oily, volatile, hygroscopic liquid that is sensitive to light and air. Chemical and physical properties of nicotine present a number of processing and stability issues. For example, because nicotine is volatile, it may evaporate during its incorporation into a gum or lozenge. In an effort to reduce potential processing and stability issues associated with the nicotine compound, a number of nicotine complexes have been developed. For example, one method includes the preparation of a complex of nicotine and an ion exchange resin. A well-known complex that is currently used in the commercially-available nicotine chewing gums is nicotine polacrilex, which is a complex of nicotine and the cation exchange resin AMBERLITE 164.